Solar Terrestrial Relations Observatory mission [1]} is the first ever space mission onboard the Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) to observe the inner heliosphere from photosphere to the complete vicinity of our Earth.
The STEREO mission includes two identical refrigerator sized spacecrafts: STEREO-A (ahead) and STEREO-B (behind). Both of these spacecrafts observe the Sun from two different angles in different orbits. STEREO-A spacecraft orbits moderately inside the Earth's orbit and takes 347 days to complete one revolution around the Sun. STEREO-B orbits slightly outwards to Earth's orbit and takes 387 days to complete one revolution of the Sun. In each year, both twin spacecrafts (STEREO-A and STEREO-B) move apart from each other by \(\approx \)  44\(^\circ \) . with these two different orientations of spacecrafts, STEREO provides a multi-dimensional view of the Sun from the Earth (SDO). A schematic view of the Sun observed with STEREO twin spacecrafts and from the Earth is presented in Figure REF .
